The disclosed technology relates to a process for preparing a sulfurized alkaline earth metal dodecylphenate containing a reduced amount of monomeric dodecylphenol.
Phenol-based detergents are known. Among these are phenates based on phenolic monomers, linked with sulfur bridges or alkylene bridges such as methylene linkages derived from formaldehyde. The phenolic monomers themselves are typically substituted with an aliphatic hydrocarbyl group to provide a measure of oil solubility. The hydrocarbyl groups may be alkyl groups, and, historically, dodecylphenol (or propylene tetramer-substituted phenol) has been widely used. An early reference to basic sulfurized polyvalent metal phenates is U.S. Pat. No. 2,680,096, Walker et al., Jun. 1, 1954; see also U.S. Pat. No. 3,372,116, Meinhardt, Mar. 6, 1968. Additionally, U.S. Pat. No. 3,036,971, Otto, May 29, 1962, discloses lubricating oils containing carbonated basic sulfurized calcium phenates. Its preparation includes the use of a glycol containing less than 6 carbon atoms.
U.S. Pat. No. 3,464,970, Sakai et al., Sep. 2, 1969, similarly discloses an overbased sulfurized calcium phenate by heating a mixture of phenolic compounds, dihydric alcohol, elementary sulfur and calcium compounds. Somewhat later, U.S. Pat. No. 5,024,773, Liston, Jun. 18, 1991, discloses a method of preparing group II metal overbased sulfurized alkylphenols involving use of a sulfurization catalyst. The product is said to have lower crude sediment, higher Total Base Number, and lower viscosity. EP 601721, Ethyl Petroleum, Jun. 15, 1994, discloses a process for preparing overbased phenates.
Recently, however, certain alkylphenols and products prepared from them have come under increased scrutiny due to their association as potential endocrine disruptive materials. In particular, alkylphenol detergents which are based on oligomers of C12 alkyl phenols may contain residual monomeric C12 alkyl phenol species. There is interest, therefore, in developing alkyl-substituted phenate detergents, for uses in lubricants, fuels, and as industrial additives, which contain a reduced amount of dodecylphenol component.
There have been several efforts to prepare phenate detergents that do not contain C12 alkyl phenols or contain reduced amounts of such materials. In some cases these efforts have involved avoiding or minimizing the presence of C12 alkylphenol as a reactant. For instance, U.S. Pat. No. 7,435,709, Stonebraker et al., Oct. 14, 2008, discloses a linear alkylphenol-derived detergent substantially free of endocrine disruptive chemicals. It comprises a salt of a reaction product of (1) an olefin having at least 10 carbon atoms, where greater than 90 mole % of the olefin is a linear C20-C30 n-alpha olefin, and wherein less than 10 mole % of the olefin is a linear olefin of less than 20 carbon atoms, and less than 5 mole % of the olefin a branched chain olefin of 18 carbons or less, and (2) a hydroxyaromatic compound.
U.S. Application 2011/0190185, Sinquin et al., Aug. 4, 2011, discloses an overbased salt of an oligomerized alkylhydroxyaromatic compound. The alkyl group is derived from an olefin mixture comprising propylene oligomers having an initial boiling point of at least about 195° C. and a final boiling point of greater than 325° C. The propylene oligomers may contain a distribution of carbon atoms that comprise at least about 50 weight percent of C14 to C20 carbon atoms.
U.S. Application 2011/0124539, Sinquin et al., May 26, 2011, discloses an overbased, sulfurized salt of an alkylated hydroxyaromatic compound. The alkyl substituent is a residue of at least one isomerized olefin having from 15 to about 99 wt. % branching. The hydroxyaromatic compound may be phenol, cresols, xylenols, or mixtures thereof.
U.S. Application 2011/0118160, Campbell et al., May 19, 2011, discloses an alkylated hydroxyaromatic compound substantially free of endocrine disruptive chemicals. An alkylated hydroxyaromatic compound is prepared by reacting a hydroxyaromatic compound with at least one branched olefinic propylene oligomer having from about 20 to about 80 carbon atoms. Suitable hydroxyaromatic compounds include phenol, catechol, resorcinol, hydroquinone, pyrogallol, cresol, and the like.
U.S. Provisional Application Ser. No. 61/549,286, Cook et al., filed Oct. 20, 2011, discloses other bridged hydrocarbyl- (e.g., alkyl-) phenol compounds and their salts, free from or substantially free from C-12 alkyl phenol moieties.
U.S. Application 2008/0070818, Arrowsmith et al., Mar. 30, 2008, discloses a lubricating oil composition including a sulphurized overbased metal phenate detergent prepared from a C9-C15 alkyl phenol, a sulphurizing agent, a metal, and an overbasing agent. The detergent includes less than 6.0% by combined mass of unsulphurized C9-C15 alkyl phenol and unsulphurized metal salts thereof. The detergent may also include a further surfactant. An olefin may be used to remove active sulphur from the sulphurized C9-C15 alkyl substituted phenol. The lubricating oil composition is said to exhibit an improved rate of acid neutralization.
U.S. Application 2007-049508, Stonebreaker et al., Mar. 1, 2007, discloses a linear alkylphenol-derived detergent substantially free of endocrine disruptive chemicals. A hydroxyaromatic compound is reacted with an olefin having at least 10 carbon atoms. Greater than 80 mole % of the olefin is a linear C20-C30 n-alpha olefin; less than 10 mole % of the olefin is a linear olefin of less than 20 carbon atoms, and less than 5 mole % of the olefin is branched chain olefin of 18 carbons or less.
U.S. Application 2008-0269351, Campbell, Oct. 30, 2008, discloses an alkylated hydroxyaromatic compound prepared by reacting a hydroxy aromatic compound with a branched olefin oligomer having from about 20 to about 80 atoms.
U.S. Application 2010-029527, Campbell et al., Feb. 4, 2010, discloses an overbased salt of an oligomerized alkylhydroxyaromatic compound. The alkyl group of the compound is derived from an olefin mixture comprising propylene oligomers having an initial boiling point of at least about 195° C.
The disclosed technology, provides a method for preparing phenate detergent which contains a reduced amount of monomeric dodecylphenol within an oligomeric dodecylphenol composition. The resulting phenate detergent may also have an increased amount tetramer and higher oligomers of the dodecylphenol, which may lead to further performance benefits.